1. By lowering value of R6
until you get just about same voltage across R18 and R14
you will let Q1 and Q2 have exactly same current.
2. After this
you should hopefully have around 0.0 volt at the output.
If not you will go on and adjust for ZERO output
elsewhere in circuit.
We will tell you how to do this.
But first try to set Q1 / Q2 to share the current from R6
exactly 50%-50%
until you get just about same voltage across R18 and R14
you will let Q1 and Q2 have exactly same current.
2. After this
you should hopefully have around 0.0 volt at the output.
If not you will go on and adjust for ZERO output
elsewhere in circuit.
We will tell you how to do this.
But first try to set Q1 / Q2 to share the current from R6
exactly 50%-50%
psice model & datasheets
moedl are in pspice format
mje150034
mje150035
mj15003
mj15004
bd139
they also
have models in saber ,spice2 spice3
the datasheet at www.onsemi.com
http://www.onsemi.com/pub/Collateral/BD135-D.PDF
http://www.onsemi.com/pub/Collateral/MJ15003-D.PDF
http://www.onsemi.com/pub/Collateral/MJE15034-D.PDF
moedl are in pspice format
mje150034
mje150035
mj15003
mj15004
bd139
they also
have models in saber ,spice2 spice3
the datasheet at www.onsemi.com
http://www.onsemi.com/pub/Collateral/BD135-D.PDF
http://www.onsemi.com/pub/Collateral/MJ15003-D.PDF
http://www.onsemi.com/pub/Collateral/MJE15034-D.PDF
Re: this schematic was simulated
so wont be difficult to change and adjust resistor R6
to achieve a balanced input stage
and get close to 0.00 volt at the loudspeaker output.
Just ( right- ) click on R6 ( 468 Ohm ) and set a new value.
I would guess a better value would ~220-270 Ohm
then run a new simulation
to get new voltages at your testpoints
lineup
long since I used Circuit Maker, but it is nice software!
seanmacss said:
so wont be difficult to change and adjust resistor R6
to achieve a balanced input stage
and get close to 0.00 volt at the loudspeaker output.
Just ( right- ) click on R6 ( 468 Ohm ) and set a new value.
I would guess a better value would ~220-270 Ohm
then run a new simulation
to get new voltages at your testpoints
lineup
long since I used Circuit Maker, but it is nice software!Hi Seanm,
the bias pot is in the wrong side of the Vbe multiplier.
The driver emitter resistor is far too big.
A 2ohm load on two pair of 15003/4!
Input ground reference on the chassis earth needs to be moved to the audio ground.
The input RF filter is set a bit high @ 100nS.
All the other grounds need to be moved to the audio ground not the chassis earth.
Get that long tail pair (LTP) in balance.
If C3 needs to be that big then there is something wrong with your implementation.
C12 & 13 will just about suit 4ohm speakers but the RC time constant (4r * 33mF) of 130mS should be longer than R15 & C8 @ 1S. A bit of adjustment needed here as well.
the bias pot is in the wrong side of the Vbe multiplier.
The driver emitter resistor is far too big.
A 2ohm load on two pair of 15003/4!
Input ground reference on the chassis earth needs to be moved to the audio ground.
The input RF filter is set a bit high @ 100nS.
All the other grounds need to be moved to the audio ground not the chassis earth.
Get that long tail pair (LTP) in balance.
If C3 needs to be that big then there is something wrong with your implementation.
C12 & 13 will just about suit 4ohm speakers but the RC time constant (4r * 33mF) of 130mS should be longer than R15 & C8 @ 1S. A bit of adjustment needed here as well.
iam not sure what to change transistors
iam not sure if i can find a beter transistor for q1 q2 q3 q4 q5
i wana keep them at least 80v
iam looking for ones that keep the sound qualty hifh
hi mike that before i built on a bread board sound great but
was engough watts for thanks for help than and now
no I am just at simulaton stage for this poweramp
need it to be 480 watts rms max but I wana keep at 350
iam using cpu fan heat sink with an alum 1/4 plate as the heat sinks
as far as i get it to 294 for r6 but i also change the transistor to
bc489 bbut am not sure how good they are
iam not sure if i can find a beter transistor for q1 q2 q3 q4 q5
i wana keep them at least 80v
iam looking for ones that keep the sound qualty hifh
hi mike that before i built on a bread board sound great but
was engough watts for thanks for help than and now
no I am just at simulaton stage for this poweramp
need it to be 480 watts rms max but I wana keep at 350
iam using cpu fan heat sink with an alum 1/4 plate as the heat sinks
as far as i get it to 294 for r6 but i also change the transistor to
bc489 bbut am not sure how good they are
Re: iam not sure what to change transistors
BC489 - high current NPN transistor ( my datasheeet is from OnSemi )
Max 80 Volt, 0.625 Watt, 0.5 Ampere, TO-92
----------------------
Quite alright transistors for this Power Amp design, if you ask me.
There are those with higher gain and lower noise, but not many for 80Volt.
For your amplifier you should stay with 80 Volts transistors, for have some margin.
I would keep those, at least for input Q1/Q2 pair and be happy!
294 Ohm for R6
in constant current source, CCS, giving curren to Q1/Q2
is very correct. ( my guess was ~220-270 Ohm )
For the second stage and output, you need transistors with even higher voltage
but this is another story.
Output Motorola MJ15003 / MJ15004 has been used many hifi power amplifiers before.
Good TO3 power transistors, that can survive a lot of heat.
I would say this is a good choice for this high power amplifier.
Motorola makes good transistors.
Metal TO3 are heavy duty devices.
Some plastic devices can require you are careful when screw to heatsink.
You cant just use too much force onto plastic case transistors,
when try to make maximal contact to heatsink.
lineup
seanmacss said:
BC489 - high current NPN transistor ( my datasheeet is from OnSemi )
Max 80 Volt, 0.625 Watt, 0.5 Ampere, TO-92
----------------------
Quite alright transistors for this Power Amp design, if you ask me.
There are those with higher gain and lower noise, but not many for 80Volt.
For your amplifier you should stay with 80 Volts transistors, for have some margin.
I would keep those, at least for input Q1/Q2 pair and be happy!
294 Ohm for R6
in constant current source, CCS, giving curren to Q1/Q2
is very correct. ( my guess was ~220-270 Ohm )
For the second stage and output, you need transistors with even higher voltage
but this is another story.
Output Motorola MJ15003 / MJ15004 has been used many hifi power amplifiers before.
Good TO3 power transistors, that can survive a lot of heat.
I would say this is a good choice for this high power amplifier.
Motorola makes good transistors.
Metal TO3 are heavy duty devices.
Some plastic devices can require you are careful when screw to heatsink.
You cant just use too much force onto plastic case transistors,
when try to make maximal contact to heatsink.
lineup
Hi Sean,
you sent an unsolicited Email saying you had made a lot of changes to your proposal.
Where?
I made nine suggestions and you have implemented one and moved towards balance in the LTP but by changing the current flow. If the amp proved to be stable at the old LTP tail current then it would be more appropriate to change the Collector load resistor.
Why have you used a high capacitance transistor in the VAS stage? It should be a low capacitance transistor. Try 2sc3423 for upper (VAS) and 2sa1360 for lower (CCS). That makes ten suggestions for improvements to your amplifier that
What about 2sc2547 for the LTP? There are lots of other low current, high gain, high linearity, high fT, high voltage, cheaper transistors than my suggestion.
you sent an unsolicited Email saying you had made a lot of changes to your proposal.
Where?
I made nine suggestions and you have implemented one and moved towards balance in the LTP but by changing the current flow. If the amp proved to be stable at the old LTP tail current then it would be more appropriate to change the Collector load resistor.
Why have you used a high capacitance transistor in the VAS stage? It should be a low capacitance transistor. Try 2sc3423 for upper (VAS) and 2sa1360 for lower (CCS). That makes ten suggestions for improvements to your amplifier that
is that so?
What about 2sc2547 for the LTP? There are lots of other low current, high gain, high linearity, high fT, high voltage, cheaper transistors than my suggestion.
Re: how can you tell
if there is no value for noise in datasheet
is because it is not very interesting characteristic for device normal use,
or the value is nothing brag about
because a low noise transistor is presented as
having low noise as one merit
while a power transistor is told to be good for power
and several ways to show this in datasheet
seanmacss said:
if there is no value for noise in datasheet
is because it is not very interesting characteristic for device normal use,
or the value is nothing brag about
because a low noise transistor is presented as
having low noise as one merit
while a power transistor is told to be good for power
and several ways to show this in datasheet
Hi Seanmacs,
can I point you to some arithmetic to show the falacy of using 2pair of MJ15003/4 to drive 4 parallel connected 8ohm speakers.
The peak voltage from your amp into 2r will be about 50Vpk.
The peak current will be about 50/2 = 25Apk.
This will be supplied by 2 devices each passing about 12.5Apk.
The gain of the 15003 is not specified at 12.5A nor guaranteed. The data does show that this current can be supplied by the transistor IF it is kept cool and IF the Vce0 is ALSO kept low. We will come back to this later.
The gain is specified as 25 @ 5A. It could be assumed that the gain @ 12.5A would fall to about 10.
Using this guessed gain value we can calculate the sum of the two base currents.
Ib~=25/10=2.5Apk
Now consider the drivers.
Using the data for the MJE15034/5 we see a gain of 10 @ 2A.
Again we can assume a lower gain @ 2.5Apk.
Let's guess at 8 @2.5Apk.
Ib=2.5/8=312mA.
The VAS needs to supply 312mApk to feed the driver with enough base current to supply 2.5Apk emitter current to then feed the output stage to deliver 25Apk to the load. This is about 600W into 2r.
Now let's look at the voltage drop across R9 (100r).
312mApk generates a drop of 31.2Vpk across R9. That in turn demands a voltage drop across R1 of about 32Vpk. That implies a current through the collector load of about 18mA. Where is this going to sink to?
2r load will not work with your proposal.
Now you need to look at SOA for each stage.
To drive a reactive speaker you can assume that the maximum current will NOT coincide with maximum output voltage. If the load shows 45 to 60 degrees of phase angle to the amplifier then it can be shown that the Vce of the devices is about equal to the Vrail voltage when the device is delivering maximum current to the load. Using the 12.5Apk value for the 4 speakers and the Vrail=65V then the device dissipation will be about 800W into a reactive load. Which part of the device does the data sheet show to survive this overload. In my opinion the only bit to survive will be the plate around the bolt holes fixing the device to the heatsink. All the semi is likely to be vapourised after thermal runaway has caused the device to go short circuit.
Have I made my point?
Now apply the same loading conditions to all the earlier devices that have to support driving the reactive load.
I think your porposal will not even work into 2 parallel connected 8ohm speakers.
Do the numbers and prove me wrong!!!!
If you cannot do the numbers with any confidence then do the research BEFORE you start designing a 600W amplifier.
can I point you to some arithmetic to show the falacy of using 2pair of MJ15003/4 to drive 4 parallel connected 8ohm speakers.
The peak voltage from your amp into 2r will be about 50Vpk.
The peak current will be about 50/2 = 25Apk.
This will be supplied by 2 devices each passing about 12.5Apk.
The gain of the 15003 is not specified at 12.5A nor guaranteed. The data does show that this current can be supplied by the transistor IF it is kept cool and IF the Vce0 is ALSO kept low. We will come back to this later.
The gain is specified as 25 @ 5A. It could be assumed that the gain @ 12.5A would fall to about 10.
Using this guessed gain value we can calculate the sum of the two base currents.
Ib~=25/10=2.5Apk
Now consider the drivers.
Using the data for the MJE15034/5 we see a gain of 10 @ 2A.
Again we can assume a lower gain @ 2.5Apk.
Let's guess at 8 @2.5Apk.
Ib=2.5/8=312mA.
The VAS needs to supply 312mApk to feed the driver with enough base current to supply 2.5Apk emitter current to then feed the output stage to deliver 25Apk to the load. This is about 600W into 2r.
Now let's look at the voltage drop across R9 (100r).
312mApk generates a drop of 31.2Vpk across R9. That in turn demands a voltage drop across R1 of about 32Vpk. That implies a current through the collector load of about 18mA. Where is this going to sink to?
2r load will not work with your proposal.
Now you need to look at SOA for each stage.
To drive a reactive speaker you can assume that the maximum current will NOT coincide with maximum output voltage. If the load shows 45 to 60 degrees of phase angle to the amplifier then it can be shown that the Vce of the devices is about equal to the Vrail voltage when the device is delivering maximum current to the load. Using the 12.5Apk value for the 4 speakers and the Vrail=65V then the device dissipation will be about 800W into a reactive load. Which part of the device does the data sheet show to survive this overload. In my opinion the only bit to survive will be the plate around the bolt holes fixing the device to the heatsink. All the semi is likely to be vapourised after thermal runaway has caused the device to go short circuit.
Have I made my point?
Now apply the same loading conditions to all the earlier devices that have to support driving the reactive load.
I think your porposal will not even work into 2 parallel connected 8ohm speakers.
Do the numbers and prove me wrong!!!!
If you cannot do the numbers with any confidence then do the research BEFORE you start designing a 600W amplifier.
AndrewT
has shown that uyou need to change a lot before you can dream of 350 Watt from your circuit.
He did not make a short summary or conclusion at the end of his article.
But if I read him correcly in my quick eye on his post.
- you need sveral more MJ15003 MJ15004 pairs to survive the heat
- you need more powerful drive transistors for those pairs
- you need to adjust the rest of circuit to handle this
A couple of notes from me:
MJ15003 TO3 capsule, is still a good choice
but you need more of them.
When you deal with such high power ( what is 350 watt good for
)
it is a good thing if you already in LTP input pair
start out at a higher current level.
I wouldnt mind using 5-10 mA for EACH input transistor.
And low input impedance for them. Say 5 KOhm.
( There are Nelson Pass Power amplifiers with lower input impedance than this! )
Especially if we have CD-player with good power output stage
or even better, a separate ( not passive! ) preamplifier
with proper drive capacity.
Building input stages for power amplifiers
that are less potent or similiar than some preamp input stages
or even phono RIAA amplifiers
will make design of the rest of stages in your power amplifier less easy.
At least when we talking 350 Watt - something I couldnt be less intersted in.
As you know, I am more into Mad_K SEWA - 7 watt pure Class A
as me and others wont have any use for more that a couple of watts output.
Now, if your speakers have a low sensitivity, i can understand
you try to compensate by enormous power!
If your speakers can only put out sound pressure level = 75dB per watt, or even 80dB
or
you live in a bit cold house and need some warmth from say 500-2.000 Watt
then
this project is just about perfect to go for.
for you
not for me
lineup still waits for Nelson Pass First Watt project
to be followed by the Nelson Pass First 1.000 Watt project
fotenote:
More info from Mister Pass here:
http://www.firstwatt.com/
.............. First 1 watt power amp
Is this for your kids, or what ..............
.
has shown that uyou need to change a lot before you can dream of 350 Watt from your circuit.
He did not make a short summary or conclusion at the end of his article.
But if I read him correcly in my quick eye on his post.
- you need sveral more MJ15003 MJ15004 pairs to survive the heat
- you need more powerful drive transistors for those pairs
- you need to adjust the rest of circuit to handle this
A couple of notes from me:
MJ15003 TO3 capsule, is still a good choice
but you need more of them.
When you deal with such high power ( what is 350 watt good for
)it is a good thing if you already in LTP input pair
start out at a higher current level.
I wouldnt mind using 5-10 mA for EACH input transistor.
And low input impedance for them. Say 5 KOhm.
( There are Nelson Pass Power amplifiers with lower input impedance than this! )
Especially if we have CD-player with good power output stage
or even better, a separate ( not passive! ) preamplifier
with proper drive capacity.
Building input stages for power amplifiers
that are less potent or similiar than some preamp input stages
or even phono RIAA amplifiers
will make design of the rest of stages in your power amplifier less easy.
At least when we talking 350 Watt - something I couldnt be less intersted in.
As you know, I am more into Mad_K SEWA - 7 watt pure Class A
as me and others wont have any use for more that a couple of watts output.
Now, if your speakers have a low sensitivity, i can understand
you try to compensate by enormous power!
If your speakers can only put out sound pressure level = 75dB per watt, or even 80dB
or
you live in a bit cold house and need some warmth from say 500-2.000 Watt
then
this project is just about perfect to go for.
for you
not for me
lineup
still waits for Nelson Pass First Watt projectto be followed by the Nelson Pass First 1.000 Watt project
fotenote:
An externally hosted image should be here but it was not working when we last tested it.
More info from Mister Pass here:
http://www.firstwatt.com/
.............. First 1 watt power amp
Is this for your kids, or what ...............
I think a triple darlington becomes very adequate here...
Sean, i already told you at least 5 times, skip or replace the wannabe outputprotection, it does not work and only handicaps your amp.
The fact that your amp survived the 2ohms, shows that the amp is in no way able to deliver the targeted watts.
If you really need to drive >50v into 2ohms, consider at least 10 outputpairs, and a 1kw psu per channel.
Mike
Sean, i already told you at least 5 times, skip or replace the wannabe outputprotection, it does not work and only handicaps your amp.
The fact that your amp survived the 2ohms, shows that the amp is in no way able to deliver the targeted watts.
If you really need to drive >50v into 2ohms, consider at least 10 outputpairs, and a 1kw psu per channel.
Mike
still for 350 watts
iam still for the 350 watts but will more then likly change
the ohms 4 or 8 or even 16 rather go to lowest ohm setting
after looking at thewatts for simulation it said 500 watts each
for the mj15003 and mj15004 so iam working new schematic
i only can go as high as 3 pairs of the mj15003 and mj15004
iam still for the 350 watts but will more then likly change
the ohms 4 or 8 or even 16 rather go to lowest ohm setting
after looking at thewatts for simulation it said 500 watts each
for the mj15003 and mj15004 so iam working new schematic
i only can go as high as 3 pairs of the mj15003 and mj15004
can anyone refer me
can anyone refer some or suggest an application note or web page explain the math and the circuit
example
http://www.onsemi.com/pub/Collateral/AN485-D.PDF
but iam looking for one for the circuit am working on!
can anyone refer some or suggest an application note or web page explain the math and the circuit
example
http://www.onsemi.com/pub/Collateral/AN485-D.PDF
but iam looking for one for the circuit am working on!
Hi Sean,
go and down load Bensen's spreadsheet.
I has a link to the original article showing the hand calculation method of designing to stay inside the temperature derated SOAR into reactive loads.
Bensen's only handles FETs.
If you want a modified BJT version of the spreadsheet send me an Email.
go and down load Bensen's spreadsheet.
I has a link to the original article showing the hand calculation method of designing to stay inside the temperature derated SOAR into reactive loads.
Bensen's only handles FETs.
If you want a modified BJT version of the spreadsheet send me an Email.
- Status
- This old topic is closed. If you want to reopen this topic, contact a moderator using the "Report Post" button.